Don't reload setting view controller if it has been dismissed

If the setting view controller is being reloaded while being dismissed,
a new SigninPromoViewMediator is created. This new one is not properly
released. -[SigninPromoViewMediator signinPromoViewRemoved] has to be
called before dealloc.

stack trace:
-[SettingsCollectionViewController loadModel]
...
-[SettingsCollectionViewController didFinishSignin:]
...
-[SigninInteractionController cancel]
-[SettingsCollectionViewController settingsWillBeDismissed]
...


Bug introduced with crrev.com/2883093002
DCHECK introduced with crrev.com/c/567923

Bug: 747121
Change-Id: Ida6847e0942c5145ddc8fbd6c4681bfcc87a8904
Reviewed-on: https://chromium-review.googlesource.com/580408
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488624}

ios/chrome/browser/ui/settings/settings_collection_view_controller.mm

@@ -230,6 +230,8 @@ void SigninObserverBridge::GoogleSignedOut(const std::string& account_id,
 
   // YES if the user used at least once the sign-in promo view buttons.
   BOOL _signinStarted;
+  // YES if view has been dismissed.
+  BOOL _settingsHasBeenDismissed;
 }
 
 @property(nonatomic, readonly, weak) id<ApplicationCommands> dispatcher;
@@ -297,7 +299,8 @@ void SigninObserverBridge::GoogleSignedOut(const std::string& account_id,
 }
 
 - (void)dealloc {
-  [self stopBrowserStateServiceObservers];
+  DCHECK(_settingsHasBeenDismissed)
+      << "-settingsWillBeDismissed must be called before -dealloc";
 }
 
 - (void)stopBrowserStateServiceObservers {
@@ -1008,7 +1011,8 @@ void SigninObserverBridge::GoogleSignedOut(const std::string& account_id,
   _signinInteractionController = nil;
   // The sign-in is done. The sign-in promo cell or account cell can be
   // reloaded.
-  [self reloadData];
+  if (!_settingsHasBeenDismissed)
+    [self reloadData];
 }
 
 #pragma mark Material Cell Catalog
@@ -1037,6 +1041,8 @@ void SigninObserverBridge::GoogleSignedOut(const std::string& account_id,
 #pragma mark SettingsControllerProtocol
 
 - (void)settingsWillBeDismissed {
+  DCHECK(!_settingsHasBeenDismissed);
+  _settingsHasBeenDismissed = YES;
   if (!_signinStarted && _signinPromoViewMediator) {
     PrefService* prefs = _browserState->GetPrefs();
     int displayedCount =

ios/chrome/browser/ui/settings/settings_navigation_controller_unittest.mm

@@ -101,6 +101,7 @@ TEST_F(SettingsNavigationControllerTest, PopController) {
         [settingsController popViewControllerAnimated:NO];
     EXPECT_NSEQ(viewController, poppedViewController);
     EXPECT_EQ(1U, [[settingsController viewControllers] count]);
+    [settingsController settingsWillBeDismissed];
   }
 }
 
@@ -116,6 +117,7 @@ TEST_F(SettingsNavigationControllerTest, DontPopRootController) {
     EXPECT_EQ(1U, [[settingsController viewControllers] count]);
 
     EXPECT_FALSE([settingsController popViewControllerAnimated:NO]);
+    [settingsController settingsWillBeDismissed];
   }
 }
 
@@ -138,6 +140,7 @@ TEST_F(SettingsNavigationControllerTest,
     [settingsController popViewControllerOrCloseSettingsAnimated:NO];
     EXPECT_EQ(1U, [[settingsController viewControllers] count]);
     EXPECT_OCMOCK_VERIFY(mockDelegate_);
+    [settingsController settingsWillBeDismissed];
   }
 }
 
@@ -156,6 +159,7 @@ TEST_F(SettingsNavigationControllerTest,
     [[mockDelegate_ expect] closeSettings];
     [settingsController popViewControllerOrCloseSettingsAnimated:NO];
     EXPECT_OCMOCK_VERIFY(mockDelegate_);
+    [settingsController settingsWillBeDismissed];
   }
 }